Structural members for which it is necessary to monitor operating condition information thereof are well-known and are used in many industries and applications. Such structural members can have a solid cross sectional construction or have an interior space. An elongated tubular member (e.g., a pipe) is an example of such a structural member with an interior space. Elongated tubular members used in offshore drilling and production systems in the oil and gas industry are a prime example of structural members for which it is necessary to monitor operating condition information thereof.
Offshore drilling and production systems include a work platform at a sea surface (i.e., a surface work platform) that is in communication with a production field beneath the seafloor. A first type of conduit, which is generally referred to a riser, is required to support equipment and materials being delivered from the surface work platform to the subsea field, and/or a conduit for lifting oil and gas being produced from the subsea field to the surface work platform. A second type of conduit, which his generally referred to as a pipeline, links wellheads to a processing site. These conduits are examples of elongated tubular members.
Many pipelines are deployed in subsea environments where water temperatures can cool the all or a portion of the pipeline that carries the hydrocarbon from the wellhead to the processing site. As hot gases that flow from the wellhead (i.e., particularly subsea wellheads) are subjected to cooling, hydrates can precipitate from the product and results in flow restrictions and in extreme cases can completely block the pipeline. In other instances, slow buildup of paraffin wax on the interior of the pipeline can cause flow restrictions. These blockages and flow restrictions pose significant risk to safe and efficient operation of such pipelines.
Tension leg platforms, floating rigs, jack-up rigs and other known offshore drilling and production systems are examples of surface work platforms. In many of these systems, in addition to the aforementioned types of conduits, some sort of legs or equivalent platform support structures extends from the sea floor to the surface work platform. These platform support structures generally have a tubular construction and are, thus, another example of a tubular structural member.
A tension leg platform (TLP) is a specific example of a surface work platform having conduits and platform support structures (i.e., tubular structural members) for which operating conditions need to be monitored. A TLP, which is a permanently positioned structure used for the production of oil and gas in offshore environments, uses platform support structures in the form of tension legs (i.e., also referred to as tendons) to support the platform above the sea surface. TLPs, which are typically used in water depths ranging from 1000 to 5000 feet, are secured in place using tension legs that each have a first end attached to a respective portion (e.g., corner) of a platform portion of the TLP and that have a second end that is attached to a respective piling that has been driven into the sea floor. Tension legs of a TLP are typically made of tubular steel. In order for the TLP to work properly, the tension legs are kept under a relatively high level of tension. Such implementation of the tension legs restricts vertical motion of the platform that would otherwise occur due to tides and wave action. A major advantage of TLPs is that the wellhead can be placed on the surface rather than on the sea floor, thereby giving better access and simpler production control.
In a typical TLP installation, three load sensors are installed into the tendon top connector assembly, which is on a sub-platform or bridge for each tendon, below the primary work platform. The data from these load sensors is then used to calculate the maximum, minimum and mean tensions and standard deviation in the tendon, together with the bending movement angle. Historically, the load cells are unreliable and often fail early in their service life such as due to their exposure to seawater and other harsh environmental conditions.
Elongated tubular members such as tension legs, risers and pipelines are subject to environmental conditions such as the flow, wave action and temperature of the surrounding seawater. These environmental conditions effect operating conditions such as, for example, tension, bending, compressive forces, expansion and contraction due to changes in water temperature, internal pressure of fluids within the risers, and other operating conditions strains and stresses to which the elongated tubular members are subjected. To ensure safe and reliable operation of such elongated tubular members, an operating condition monitoring system is required to provide reliable measurement of operating condition information in each of the elongated tubular members and output such operating condition information, preferably in real-time. When the monitoring system fails, it is often necessary to shut down the drilling or production system at significant expense such has due to lost revenue and loss of drilling or production time
As is well-known, it is desirable to operate drilling and production systems in a safe, reliable, predictable and efficient manner. To this end, it is beneficial to monitor operating condition information of elongated tubular members of such drilling and production systems, whether offshore-based or land-based. Examples of operating condition include, but are not limited to, strain within a wall of an elongated tubular members, pressure within an interior space of the elongated tubular members, torsion applied to the elongated tubular members, temperature of the wall or surface of the elongated tubular members, temperature of a fluid within the interior space of the elongated tubular members, and flow confirmation of a fluid within the interior space of the elongated tubular members.
Various devices and systems have been deployed to generate and monitor operating condition information. Examples of these devices and systems include, but are not limited to, load cells on TLP tension legs, mechanical strain gauges on risers and pipelines, invasive sensors on risers and pipelines (e.g., which penetrate the conduit), and other types of devices and systems. These types of prior art devices and systems are of limited functional value in that they provide less than optimal operating condition information, are subject to early fatigue caused by the rigorous environmental conditions in which they are employed, and often undesirably require invasive installation techniques.
Therefore, apparatuses, systems and sensor housing assemblies that utilize fiber optic sensors for enabling monitoring of operating condition information within one or more elongated tubular members to overcome drawbacks associated with conventional approaches for generating and monitoring operating condition information would be advantageous, desirable and useful.